THE FINITE UNIVERSE 



est visible rays. The Rontgen rays probably lie 

 out beyond these invisible ultra-violet waves. 

 Likely it will not be very long before some ingeni- 

 ous way will be found to measure their period or 

 frequency, and then we shall know their wave- 

 length or lengths ; for the Rontgen light might be 

 compounded of a variety of waves, just as white 

 light is. It may turn out a whole new " octave " of 

 light. 



But what is most interesting in all this is that 

 this unexpected apparition in the field of physics 

 fits in with the ether theory, just as did the Hertz- 

 waves, whose arrival was expected. In order to ac- 

 count for the known actions of light, the founders 

 of the wave theory, Young and Fresnel, were led 

 to assume the existence of this highly tenuous me- 

 dium filling all space. It was not long before it 

 was found that heat radiations also have a wave 

 form and travel at the same unthinkable pace. 

 Likewise the action of a magnet, and also of an 

 electric " field," is very easily accounted on the sup- 

 position of a disturbance in this same medium. It 

 may be noted that the remarkable discovery in 1892 

 by a young Hollander, Zeeman, as to the effect of a 

 magnet on light, tends to confirm this view. It was, 

 like the Hertz discovery, the result of a prediction 

 from the inferred properties of the ether. 



When these and a number of minor results are 

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